1. Field of the Invention
The technical field of the invention is a process for an application of sealant (so-called xe2x80x9ccompoundxe2x80x9d) to a body hook of a body of a metal can.
2. Prior Art
Prior art realizes sealings on metal packings such that a sealant, which is usually provided on the basis of a rubber preparation or a synthetic caoutchouc, is dispersed in water or organic solvents (SBC or WBC) and introduced into the end hook of a can end or into the fold edge of a can base with a spraying gun. Subsequently, the water or the solvent(mixture) has to be evaporated and the dried seal has to be stored at least 24 hours before closing the can end and the can body (compare DE-A 27 27 628 or U.S. Pat. No. 4,201,308). In the prior art process, the quantity of sealant used is subject to a statistical variation, the effectively introduced or applied sealant depending to a considerable degree on the viscosity, which in turn depends on the temperature. Consequently, the temperature determines the quantity of sealant introduced, namely the circumferential distribution of sealant as well as the thickness of the sealant introduced.
It is an object of the present invention to improve the processes for introduction or application of sealant previously used, particularly with regard to their precision and reproducibility. The objective is to make the quantity of sealant applied or introduced independent on external influences to such a degree that it may be positioned more precisely to permit on a long-term basis the saving of considerable quantities of sealant.
Said object is achieved by applying a sealant to the body hook of a can body and not to a can end, said application being effected before flanging the seam, which particularly is a double seam.
By realizing the inventive idea, a frequent control of the sealant is not required, the can body itself being dipped from above into the sealant or contacting it to such a degree that only the portion of the body hook is wetted with said sealant. Compared to prior art, the inventive process permits a better positioning and therefore, a more precise application and consequently a more economizing dosing of the sealant. Thus a considerable quantity of sealant is saved over a fairly long time. Due to the invention, defects in the rubber-coating of can ends are a thing of the past.
To fluidize the raw sealant, it is softened (fluidized), usually by an extruder or compounder. The compound may then be transferred on a gravure roller which may be supplied by a sheet die, however, said sheet die itself also being able to provide the fluidal compound without using a deep-draw roller1, said compound presenting a certain minimum dipping depth; said minimum depth may be controlled (claim 3).
1. German term xe2x80x9cTiefziehwalzexe2x80x9d (=deep-draw roller) must obviously read correctly xe2x80x9cTiefdruckwalzexe2x80x9d (=gravure roller). 
Also, time, speed and dipping depth of the dipping movement of the body hook may be controlled.
The application of compound on the seam portion of the can body (body hook) is improved with regard to uniformity by rotating said can body in the indicated direction xcex1, (alpha) around its own axis at least when it contacts or is dipped into the sealant. For this purpose, a magnetic drive (for soft metal2 cans) may be provided.
2. German term xe2x80x9cWeichblechdosenxe2x80x9d (=soft metal cans) is an obvious typing error. The correct term is xe2x80x9cWeigblechdosenxe2x80x9d (=tin plate cans). 
By combining a dipping movement in vertically downward direction and a rotatory movement around the axis, a high degree of uniformity of sealant on the body hook is achieved, simultaneously permitting a precise positioning and dosing and thus savings of largest possible quantities of sealant to achieve smallest necessary quantities of sealant on the body hook.
In the following, the invention is described more in detail on the basis of embodiments.